JP2013044311A - Sensor arrangement structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor arrangement structure preventing the failure of a sensor by suppressing water drops from sticking to the sensor installed in an intake passage of an engine, thereby improving the reliability of an intake amount control system or the like for which the sensor is used.SOLUTION: The intake passage of an intake device 12 includes intake piping 17 provided upstream, an intake chamber 22 provided downstream of the intake piping 17 and located at the side of an engine body 11, and an intake pipe 28 leading intake air to respective cylinders 11A, 11B, 11C, 11D of the engine body 11 from the intake chamber 22. The intake piping 17 is disposed to allow intake air to flow into the intake chamber 22 from either one side in the longitudinal direction of the engine body 11, and an oxygen sensor 30 is disposed in a branch pipe 24 on the side close to the intake piping 17 out of branch pipes 24-27 provided for each cylinder to constitute the intake pipe 28.

Description

  The present invention relates to a sensor arrangement structure, and more particularly to a sensor arrangement structure in which an oxygen sensor that detects an oxygen concentration is arranged in an intake pipe of an engine.

In a diesel engine, if the amount of EGR (exhaust gas recirculation) is increased in order to reduce NOx in the exhaust gas, the moisture contained in the intake gas including the exhaust gas increases and the moisture is reduced when the intake gas is cooled. Condensates and water droplets are easily formed. If the water droplets adhere to the detection part of the oxygen sensor heated to a high temperature by the heater, the detection part may be damaged by a thermal shock, so it is necessary to prevent the water droplets from adhering to the oxygen sensor.
Since the oxygen sensor attached to the exhaust system is exposed to high-temperature exhaust gas, the temperature at the site where the oxygen sensor is installed becomes high, and there is little condensation of moisture in the exhaust gas.

  FIG. 11 shows an example in which an oxygen sensor is arranged in an intake chamber constituting an intake manifold as a conventional oxygen sensor arrangement structure. For example, Japanese Patent Application Laid-Open No. 2010-90848 discloses an oxygen concentration sensor disposed in an intake passage. Further, for example, Patent Document 2 (Japanese Patent Laid-Open No. 2003-65171) is known as an oxygen concentration sensor disposed in a surge tank.

  An engine 100 shown in FIG. 11 includes an engine body 101 provided with a plurality of cylinders, an intake device 102 connected to one side surface of the engine body 101, and an exhaust device 103 connected to the other side surface of the engine body 101. Is provided. FIG. 11 is a plan view of the engine 100.

  The intake device 102 includes an intake inlet 106 made of an air cleaner, an intercooler, and the like, an intake pipe 107 connected to the intake inlet 106, one end connected to the intake pipe 107, and the other end connected to the engine body 101. The intake manifold 108 is made up of.

  The intake manifold 108 includes a connection port 115 connected to the intake pipe 107, an intake chamber 116 adjacent to the connection port 115, and branch pipes 121 to 124 extending from the intake chamber 116 to each cylinder of the engine body 101. .

An oxygen sensor 126 that detects the oxygen concentration in the intake gas in the intake chamber 116 is attached to the upper portion of the central portion of the intake chamber 116.
The exhaust device 103 includes an exhaust manifold 111. An EGR passage 113 that connects the exhaust manifold 111 and the intake pipe 107 is provided.

  According to FIG. 1 of Patent Document 1, a multi-cylinder engine 10 includes a plurality of combustion cylinders 12 arranged in parallel in an engine body, and a straight intake passage 14 is connected to each combustion cylinder 12, thereby providing an EGR gas passage. Each branch passage 24 of 22 is connected to each intake passage 14 by an EGR gas merging portion 26, and an oxygen concentration sensor 30 is attached to the downstream side of the EGR gas merging portion 26 of each intake passage 14.

  Further, according to Patent Document 2, the surge tank 30 is provided with a sensor mounting portion 32 that is depressed toward the internal space and that protrudes into the internal space, and is accommodated in the sensor mounting portion 32. 3 shows a configuration in which the air-fuel ratio sensor 38 is assembled. In addition, an annular convex portion 50 is provided on the bottom surface 34 of the sensor mounting portion 32 to block oil and moisture flowing along the wall surface of the surge tank 30.

JP 2010-90848 A JP 2003-65171 A

  In the technique shown in FIG. 11, the temperature of the exhaust gas flowing into the intake pipe 107 via the EGR passage 113 decreases in the intake chamber 116 to which the oxygen sensor 126 is attached, and moisture contained in the intake gas including the exhaust gas. Condensates easily and water droplets are easily generated. When the moisture is generated, since the distance from the intake pipe 107 to which the outlet of the EGR passage 113 is connected to the intake chamber 116 is relatively short, water droplets adhering to the intake passage wall surface from the intake pipe 107 to the intake chamber 116 Since the amount of water is small, many water droplets are generated by cooling the intake gas in the intake chamber 116 while the amount of water droplets in the intake gas is still large. Therefore, there is a problem that the amount of water droplets attached to the oxygen sensor 126 increases.

In Patent Document 1, EGR gas passages 22 are branched into branch passages 24 corresponding to the number of cylinders, and each branch passage 24 is connected to each intake passage 14 so that moisture in the exhaust gas is divided into each intake passage 14. However, since the intake passage 14 has a straight shape, most of the water droplets formed by condensation of the moisture in the intake passage 14 are oxygen concentration sensor 30. Will adhere to.
Furthermore, since the oxygen concentration sensor 30 is mounted horizontally in the intake passage 14, for example, water drops that fall along the inner wall surface of the intake passage 14 due to gravity tend to adhere to the detection element of the oxygen concentration sensor 30. .

Further, in Patent Document 2, it is shown that an annular convex portion 50 is provided on the lower surface 34 of the sensor mounting portion 32 to block oil and moisture flowing along the wall surface of the surge tank 30, but the surge tank 30 is often provided at a position close to the connection of the outlet of the EGR passage 113 and the connection of the passage for purging vapor (steam fuel), so that oil and moisture flowing along the wall surface of the surge tank 30 are removed from the surge tank. There are more intake passages to the respective downstream cylinders.
Accordingly, as in the case described with reference to FIG. 11, there is a problem that the amount of water droplets adhering to the air-fuel ratio sensor disposed in the surge tank increases, so that only the annular protrusion 50 disclosed in Patent Document 2 is a sufficient countermeasure. It is difficult to obtain the effect.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sensor arrangement structure that prevents adhesion of water droplets to a sensor installed in an intake passage of an engine to prevent sensor failure and improves the reliability of a system in which the sensor is used. There is.

  In order to achieve the above object, the present invention provides a sensor arrangement structure in which a sensor for measuring an air-fuel ratio in intake air is arranged in an intake passage of an engine, wherein the intake passage includes an intake pipe provided upstream, A plurality of branch pipes that are provided on the downstream side of the intake pipe and communicate with each intake port of the engine to form a branch passage, and an intake manifold having a collection portion to which the branch pipes are connected; However, it is arranged so as to be connected to the collecting portion from one side in the branch passage arrangement direction, and a sensor is arranged in the intake passage on the one side downstream of the intake pipe.

  According to the present invention, the intake pipe is arranged so as to be connected to the collecting portion from one side in the branch passage arrangement direction, and downstream of the intake pipe that includes the collecting portion and reaches the intake port of the engine. Among the intake passages, a sensor is arranged in the intake passage on the one side. That is, the sensor is installed at the position on the one side in the branch passage or collecting portion (intake chamber) on the one side.

In the branch passage on the side (one side) where the intake pipe is connected to the collective part (intake chamber) or in the collective part, the intake air enters the collective part from the intake pipe and from there to the main flow toward the engine intake port It becomes a relationship that is located. Therefore, since the main flow flows in a straight line direction due to inertia, it flows in a wraparound relationship, and the water droplets contained in the intake air adhere to the inner wall of the intake passage on the way and branch on one side of the branch passage arrangement direction. It becomes difficult to reach the passage.
Therefore, for example, it is possible to suppress water droplets from adhering to the oxygen sensor by disposing the oxygen sensor on the one side of the intake passage. As a result, it is possible to prevent the sensor from being damaged due to the attachment of water droplets and improve the reliability of the intake air amount control system in which the sensor is used.
The intake air means only fresh air or both of which EGR gas is added to fresh air.

  Preferably, in the present invention, the one side branch passage is formed with a bent portion that is bent so as to project outward from the collecting portion toward the engine in the branch passage arrangement direction. It is good to arrange | position offset from the axis line which passes along the center of a channel | path at the inner peripheral side of the said bending part.

According to such a configuration, by disposing the sensor offset from the axis passing through the center of the branch passage toward the inner peripheral side of the bent portion, the main flow in the branch passage becomes difficult to hit the sensor, and water droplets also hardly hit the sensor.
In other words, water drops tend to go straight with the inertia at the bent part, so it is easy to hit the outer wall on the outer periphery side of the branch passage, and it is difficult for it to travel to the inner periphery side of the branch passage. Water drops are difficult to hit.

In the present invention, it is preferable that the sensor is arranged at a terminal portion near the engine in each branch passage.
According to such a configuration, since water droplets flowing through the intake passage adhere to the inner wall in each part of the intake passage, the water droplets are almost eliminated at the end of the branch passage that is the most downstream of the intake passage, and the sensor is hardly affected by the water droplets. .
Further, since the end portion is closest to the combustion chamber of the engine in the intake passage, data effective in controlling the combustion of the engine can be detected.

Preferably, in the present invention, the intake pipe composed of a plurality of branch passages is provided with a plurality of branches, and the sensor is disposed in a branch section on the second and subsequent stages from the upstream side of the intake pipe. Good.
According to such a configuration, water droplets generated by condensation of moisture in the intake gas adhere to the wall surface of the first-stage branch passage of the intake pipe, and the water drops are reduced in the second-stage and subsequent branch passages. It can be made difficult to adhere.

In the present invention, it is preferable that the sensor is a branch pipe branched from the second and subsequent branch sections, and is arranged in a branch pipe on the center side in the branch passage arrangement direction.
According to such a configuration, since the main flow in the intake pipe tends to go straight by inertia, it is difficult for the main flow to travel to the branch passage from the branch portion to the center side in the branch passage arrangement direction. Adhesion to can be further reduced.

As described above, according to the present invention, the intake pipe is disposed so as to be connected to the collective portion from one side in the branch passage arrangement direction, and the intake pipe that includes the collective portion and reaches the intake port of the engine. A sensor is arranged in the intake passage on the one side among the intake passages downstream of the intake passage.
Since the mainstream flows in a straight line due to inertia, the sensor flows so as to flow around, and water droplets contained in the intake air are attached to the inner wall of the intake passage on the way and located on one side of the branch passage arrangement direction. It becomes difficult to reach the branch passage.
Therefore, for example, by disposing the oxygen sensor on the one side of the intake passage, it is possible to prevent water droplets from adhering to the oxygen sensor and prevent the internal elements of the oxygen sensor from being cracked. As a result, sensor failure is prevented. In addition, the reliability of the intake air amount control system in which the sensor is used can be improved.

It is a top view of the engine explaining the sensor arrangement structure (1st embodiment) concerning the present invention. It is a side view (partial sectional view) of an engine for explaining a sensor arrangement structure (first embodiment) according to the present invention. It is explanatory drawing (1st Embodiment) explaining arrangement | positioning of the sensor to the engine intake system which concerns on this invention. 4 is a cross-sectional view taken along line 4-4 of FIG. 3 (first embodiment), FIG. 4A is a cross-sectional view of a round pipe-like branch pipe, and FIG. 4B is a cross-sectional view of a square pipe-like branch pipe. FIG. 5A is an operation diagram showing the operation of the sensor arrangement structure according to the present invention (first embodiment), FIG. 5A is an operation diagram showing the flow of intake gas, and FIG. 5B is a diagram of water droplets on the inner wall of the branch pipe. It is an effect | action figure which shows adhesion. It is a top view of the engine explaining the sensor arrangement structure (second embodiment) according to the present invention. It is a principal part enlarged plan view of the sensor arrangement structure (2nd Embodiment) which concerns on this invention. It is an effect | action figure which shows the effect | action of the sensor arrangement structure (2nd Embodiment) which concerns on this invention. It is a principal part top view of the engine explaining the modification of the sensor arrangement structure (2nd Embodiment) which concerns on this invention. It is a top view of the engine explaining the sensor arrangement structure (3rd embodiment) concerning the present invention. It is a top view of the engine explaining the conventional sensor arrangement structure.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

(First embodiment)
As shown in FIG. 1, an engine 10 includes an engine main body 11 including a cylinder block, a cylinder head, and the like, an intake device 12 connected to one side of the cylinder head of the engine main body 11, and the other side of the cylinder head of the engine main body 11. It is an in-line four-cylinder diesel engine provided with the exhaust apparatus 13 connected to.

The engine body 11 is provided with a first cylinder 11A, a second cylinder 11B, a third cylinder 11C, and a fourth cylinder 11D.
The intake device 12 includes an intake inlet portion 16 composed of an air cleaner, an intercooler, and the like, an intake pipe 17 connected to the intake inlet portion 16 and extending substantially parallel to the longitudinal direction of the engine body 11, and one end portion of the intake pipe 17. The intake manifold 18 is connected to the engine body 11 at the other end.

The intake manifold 18 includes a connection end 21 connected to the end of the intake pipe 17, an intake chamber 22 adjacent to the connection end 21 and positioned on the side of the engine body 11, and the intake chamber 22 to the engine. This is an integrally molded product comprising branch pipes 24 to 27 that extend to the main body 11 and supply intake air to the cylinders provided in the engine main body 11.
These branch pipes 24 to 27 constitute four intake pipes 28.
As described above, “intake” refers to a gas sucked into the engine 10 and refers to fresh air only or fresh air plus gas returned by EGR.

The intake pipe 17 is arranged so that intake gas flows into the intake chamber 22 from either side of the engine body 11 in the longitudinal direction via the intake inlet portion 16.
Of the four branch pipes 24 to 27, an oxygen sensor (linear A / F sensor) 30 for detecting the oxygen concentration in the intake gas is attached to the branch pipe 24 of the first cylinder 11A closer to the intake pipe 17. ing. Thus, one of the main reasons for attaching the oxygen sensor 30 to the branch pipe 24 is that the branch pipe 24 is farthest from the intake pipe 17, and the intake gas flowing through the intake passage in the intake device 12 is the most. This is because the position makes a detour.

  The cylinder corresponding to the branch pipe 24 to which the oxygen sensor 30 is attached is the first cylinder 11A here, but when the intake pipe 17 is located on the lower side in the longitudinal direction of the engine body 11 in FIG. An oxygen sensor is attached to the branch pipe 27 of the fourth cylinder 11D. In short, the oxygen sensor 30 is attached to the branch pipe corresponding to the endmost cylinder.

  Further, for example, in the case of a V-type 6-cylinder engine, the first to third cylinders are provided in one bank and the fourth to sixth cylinders are provided in the other bank. When installed with the arrangement relationship of the intake pipes 17 as shown in FIG. 1, the first cylinder, the third cylinder, the fourth cylinder, which are the endmost cylinders, as in the inline four-cylinder engine 10 described above. An oxygen sensor 30 is attached to a branch pipe corresponding to any one of the cylinder and the sixth cylinder.

  The exhaust device 13 includes an exhaust manifold 33, and the exhaust manifold 33 and the end of the intake pipe 17 are connected by an EGR passage 34, so that the exhaust gas in the exhaust manifold 33 is reduced in order to reduce NOx in the exhaust gas. Is returned to the intake pipe 17 via the EGR passage 34.

  As shown in FIG. 2, the oxygen sensor 30 is attached to the end portion of the branch pipe 24 on the engine body 11 side by being inserted vertically from the top to the bottom, and attached to a detection unit 30 b provided at the tip of the oxygen sensor 30. Then, the oxygen concentration of the intake gas flowing through the branch pipe 24 is detected. The oxygen sensor 30 is not limited to an example in which the internal element is positioned below the attachment point and is not necessarily inserted in the vertical direction. For example, it may be attached to the branch pipe 24 while being inclined downward.

As shown in FIG. 3, the branch pipe 24 includes an upstream straight pipe portion 24 a extending obliquely and linearly from the intake chamber 22 to one end side of the engine main body 11, and the tip of the upstream straight pipe portion 24 a. 11 and a downstream straight pipe part 24c that extends linearly from the tip of the bent pipe part 24b and is connected almost perpendicularly to the side surface of the cylinder head of the engine body 11. .
The branch pipe 24 composed of the upstream straight pipe portion 24a, the bent pipe portion 24b, and the downstream straight pipe portion 24c as a whole protrudes from the intake chamber 22 toward the engine body 11 toward the outside of the engine in the longitudinal direction of the engine. It has a shape in which a bent portion to be bent is formed.

  The oxygen sensor 30 is bent with respect to an axis 24d that is provided in the branch pipe 24 near the downstream straight pipe section 24c of the bent pipe section 24b or in the downstream straight pipe section 24c and passes through the center of the branch pipe 24. The branch pipe 24 is offset from the inner peripheral side.

  As shown in FIG. 4A, in detail, the vertical pipe passing through the round pipe-like branch pipe 24 passes through an axis 24d of the branch pipe 24 (a line extending in the front-and-back direction of the paper surface, which is indicated by a black circle here). The oxygen sensor 30 is inserted and attached from the top to the bottom at a position offset from the line 40 by the offset amount e. The allowable inclination angle θ with respect to the vertical line 40 is 0 to 45 °.

The oxygen sensor 30 includes a body 30a attached to the branch pipe 24 and a detection unit 30b provided at the tip of the body 30a.
The oxygen sensor 30 is attached to the branch pipe 24 by, for example, screw coupling between the male screw formed on the outer peripheral surface of the body 30a of the oxygen sensor 30 and the screw formed on the branch pipe 24.
As shown in FIG. 4B, a square pipe-like branch pipe 25 may be used instead of the branch pipe 24.

For example, when the oxygen sensor is attached to the side of the branch pipe so as to extend in the horizontal direction, water droplets that fall on the inner wall surface of the branch pipe and fall due to gravity are likely to adhere to the oxygen sensor. By attaching the oxygen sensor 30 to the upper part of the branch pipe 24 so as to extend in the vertical direction, it is possible to prevent water droplets from adhering to the oxygen sensor 30 as described above.
Since the oxygen sensor 30 is arranged in the substantially vertical direction from the top to the bottom, the water droplets transmitted to the internal elements of the oxygen sensor 30 fall on the bottom of the branch pipe 24 without staying on the oxygen sensor 30. Further, since the water droplets flow down along the inner wall surface of the branch pipe 24 formed near the oxygen sensor 30, it is difficult for water droplets to be transmitted to the internal elements of the oxygen sensor 30.

Next, the operation of the oxygen sensor arrangement structure described above will be described.
As shown in FIG. 5A, when the intake gas flows through the branch pipe 24, the intake gas travels straight in the pipe in a uniform flow as shown by the arrows in the upstream straight pipe portion 24a. In the bent pipe part 24b, the flow in the upstream straight pipe part 24a is maintained as it is due to the influence of the inertia of the intake gas.

  In addition, in the downstream side and the downstream straight pipe part 24c of the bent pipe part 24b, the intake gas flows in a state of approaching the outer peripheral side inner wall 24f of the bent branch pipe 24 as shown by the arrows, and the bent branch pipe 24 is bent. In the vicinity of the inner peripheral side inner wall 24g, a flow having a larger velocity than that on the outer peripheral side inner wall 24f side hardly occurs. The oxygen sensor 30 is disposed in the vicinity of the inner peripheral side inner wall 24g.

  Further, due to the flow of the intake gas shown in FIG. 5 (a), as shown in FIG. 5 (b), in the inner wall of the branch pipe 24, the inner peripheral side inner wall 24g has more water droplets 45 than the outer peripheral side inner wall 24f. There is little adhesion, and in particular, in the range from the downstream side of the bent pipe part 24b of the inner peripheral side inner wall 24g to the downstream straight pipe part 24c, the water droplet 45 hardly adheres.

  That is, since the oxygen sensor 30 is disposed at the outermost branch pipe 24 in the engine body 11 and at the end portion near the engine body 11, many water droplets are formed on the inner wall on the upstream side of the intake device 12 (see FIG. 1). The oxygen sensor 30 is offset to the inner peripheral side of the branch pipe 24 that is bent from the axis 24d. Therefore, the main flow in the branch pipe 24 is less likely to hit the oxygen sensor 30, and the water droplet 45 is less likely to adhere to the oxygen sensor 30.

Since the water droplet 45 advances straight due to its inertia in the bent tube portion 24b, the water droplet 45 easily hits the outer peripheral side inner wall 24f of the branch tube 24 and hardly travels to the inner peripheral side inner wall 24g side of the branch tube 24. Becomes difficult to adhere.
From the above, the oxygen sensor 30 is hardly affected by water droplets.

As described above, the second main reason for attaching the oxygen sensor 30 to the branch pipe 24 is that the branch pipe 24 corresponding to the endmost cylinder of the engine body 11 is the most among the branch pipes 24 to 27. This is because the degree of bending is increased.
If the degree of bending of the branch pipe 24 is large, as shown in FIGS. 5A and 5B, the water droplet 45 is less likely to adhere to the oxygen sensor 30, and stable oxygen concentration detection of the oxygen sensor 30 can be performed for a long time. Can be ensured over the entire range.

  Further, by attaching the oxygen sensor 30 to the branch pipe 24, for example, compared to the conventional case where the oxygen sensor is attached to the intake chamber, water droplets contained in the intake gas are divided into the branch pipes 24 to 27 and flowed. As a result, the amount of water droplets in the branch pipe 24 can be significantly reduced, making it more difficult for the water droplets to adhere to the oxygen sensor 30.

  Furthermore, by attaching the oxygen sensor 30 to the end portion of the branch pipe 24 close to the engine main body 11, the oxygen concentration is detected at a position close to the combustion chamber of the first cylinder 11 </ b> A of the engine main body 11. Since the data close to the actual condition of the oxygen concentration sucked into the combustion chamber when controlling the combustion of the fuel in the combustion chamber based on the oxygen concentration detected in (5), the accuracy of the control can be improved.

(Second Embodiment)
In the second embodiment described below, the same components as those in the first embodiment shown in FIG.
As shown in FIG. 6, the engine 50 is a four-cylinder diesel engine including an intake device 52 connected to one side of the cylinder head of the engine body 11.

The intake device 52 includes an intake manifold 58 having one end connected to the intake pipe 17 and the other end connected to the engine body 11.
The intake manifold 58 includes a connection end 21, an intake chamber 22, an intake pipe 60 that extends from the intake chamber 22 to the engine body 11 and supplies intake gas to each cylinder 11 </ b> A, 11 </ b> B, 11 </ b> C, 11 </ b> D of the engine body 11. It is an integrally molded product consisting of
An oxygen sensor 30 is attached to the intake pipe 60 at a position close to the engine body 11 and corresponding to the second cylinder 11B on the side close to the intake pipe 17.

  As shown in FIG. 7, the intake pipe 60 includes a main passage 60 </ b> A connected to the intake chamber 22, a first branch portion 61 that branches into two from this one main passage 60 </ b> A, and the first branch portion 61. The upstream branch pipes 61a and 61b divided by the second branch part 62, one of the upstream branch pipes 61a branching into two, the downstream branch pipes 62a and 62b divided by the second branch part 62, and the other upstream The third branch part 63 in which the branch pipe 61b branches in two, the downstream branch pipes 63a and 63b separated by the third branch part 63, and the communication that connects the second branch part 62 and the third branch part 63 respectively. The pipe 64 and an open / close valve 66 provided in the intermediate portion of the communication pipe 64, and the downstream branch pipes 62 a and 62 b and the downstream branch pipes 63 a and 63 b are connected to the cylinders 11 A, 11 B, 11 C, and 11 D of the engine body 11. To each of the oxygen sensors 3 Is for reasons explained in FIG. 8, is attached to the downstream branch pipe 62b communicating with the second cylinder 11B.

The communication pipe 64 and the open / close valve 66 constitute a dynamic pressure supercharging mechanism 70 that can change the amount of intake gas supplied to each cylinder by making the intake pipe effective length variable.
When the on-off valve 66 is closed during low-speed rotation of the engine, the flow of intake gas in the communication pipe 64 is shut off, and the intake pipe effective length from the throttle valve (not shown) to the end of the intake pipe 60 on the engine body 11 side. Therefore, the intake gas amount can be increased in synchronization with the pressure wave by utilizing the pulsation of the intake gas generated at the time of low speed rotation, and the low speed torque of the engine can be improved.

  Further, when the opening / closing valve 66 is opened during high-speed rotation of the engine, the communication pipe 64 becomes a bypass passage for the intake gas, and the above-described intake pipe effective length is shortened. Therefore, the intake gas pulsation generated during high-speed rotation is utilized. The amount of intake gas can be increased.

Next, the operation of the intake pipe 60 described above will be described.
In FIG. 8, when the intake gas flows from the intake chamber 22 into the main passage 60A of the intake pipe 60 as indicated by an arrow A, it is branched into two at the first branch portion 61 as indicated by arrows B and C. The upstream branch pipes 61a and 61b flow separately.

  At this time, the water droplet 45 contained in the intake gas hits and adheres to the inner side walls 61c and 61d of the upstream branch pipes 61a and 61b immediately after branching at the first branch portion 61, and further, the upstream branch pipes 61a and 61b in the middle of the flow. It also adheres to the outer walls 61e and 61f.

  Further, the intake gas continuously flows from the upstream branch pipes 61a and 61b through the second branch part 62 and the third branch part 63 to the downstream branch pipes 62a and 63b as indicated by arrows B and C due to the inertia of the intake gas. As indicated by arrows D and E, the light branches off at the second branch part 62 and the third branch part 63 and flows to the downstream branch pipes 62b and 63a.

  At this time, the water droplet 45 remaining in the intake gas flowing through the upstream branch pipes 61a and 61b tends to travel to the downstream branch pipes 62a and 63b due to inertia, but the downstream branch pipes 62b and 63a are connected to the upstream branch pipe 61a, Since it is in a deviated position with respect to 61b, the water droplet 45 is unlikely to travel to the downstream branch pipes 62b and 63a. Therefore, by arranging the oxygen sensor 30 in the downstream branch pipe 62b (or the downstream branch pipe 63a depending on the position of the intake pipe 17 (see FIG. 6)), it is possible to make it difficult for the water droplet 45 to adhere to the oxygen sensor 30.

As shown in FIG. 9, the oxygen sensor 30 may be disposed in the second branch portion 62 of the intake pipe 60 (or the third branch portion 63 depending on the position of the intake pipe 17 (see FIG. 6)).
This is because, as described with reference to FIG. 8, most of the water droplets in the intake gas adhere to the inner side walls 61c and 61d and the outer side walls 61e and 61f of the upstream branch pipes 61a and 61b immediately after the first branch part 61. This is because the number of water droplets remaining in the intake gas at the second branch portion 62 shown in FIG.

(Third embodiment)
In the third embodiment described below, the same components as those in the first embodiment shown in FIG.
As shown in FIG. 10, the engine 80 includes an engine main body 81 including a cylinder block, a cylinder head, and the like, an intake device 82 connected to one side of the cylinder head of the engine main body 81, and the other side of the cylinder head of the engine main body 81. An in-line 6-cylinder diesel engine having an exhaust device 83 connected to the engine.
The engine body 81 includes a first cylinder 81A, a second cylinder 81B, a third cylinder 81C, a fourth cylinder 81D, a fifth cylinder 81E, and a sixth cylinder 81F.

  The intake device 82 includes an intake manifold 88 having one end connected to the intake pipe 17 and the other end connected to the engine body 11.

The intake manifold 88 extends from the intake end 22, the intake chamber 22, and the intake chamber 22 to the engine body 81 to supply intake gas to the cylinders 81 </ b> A, 81 </ b> B, 81 </ b> C, 81 </ b> D, 81 </ b> E, 81 </ b> F of the engine body 81. This is an integrally molded product including the intake pipe 90.
The oxygen sensor 30 is attached to the intake pipe 90 at a position close to the engine body 81 and corresponding to the third cylinder 81C (or the first cylinder) on the side close to the intake pipe 17.

  The intake pipe 90 includes a main passage 90 </ b> A connected to the intake chamber 22, a first branch portion 91 branched from the one main passage 90 </ b> A into two, and an upstream branch pipe 91 a divided by the first branch portion 91. , 91b, a second branch part 92 in which one upstream branch pipe 91a branches into three, downstream branch pipes 92a, 92b, 92c divided by the second branch part 92, and the other upstream branch pipe 91b in three A third branch section 93 that branches into two branches, and downstream branch pipes 93a, 93b, 93c separated by the third branch section 93. The downstream branch pipes 92a, 92b, 92c and the downstream branch pipes 93a, 93b, 93c Are in communication with the cylinders 81A, 81B, 81C, 81D, 81E, 81F of the engine body 81, respectively.

  Of the three downstream branch pipes 93a, 93b, 93c, the downstream branch pipe 93b is arranged on the extension line of the upstream branch pipe 91a, so that water droplets remaining in the upstream branch pipe 91a can easily flow into the downstream branch pipe 93b. Since the inflow of water droplets into the branch pipe 93c is the least, and the water flow into the downstream branch pipe 93a is next small, the oxygen sensor 30 is connected to the downstream branch pipe 92c (or the first cylinder 81A) communicating with the third cylinder 81C. It is attached to the downstream branch pipe 92a) which communicates.

  In the first embodiment shown in FIG. 3, the branch pipe 24 is composed of an upstream straight pipe portion 24a that extends linearly, a bent pipe portion 24b that is bent, and a downstream straight pipe portion 24c that extends linearly. However, the present invention is not limited to this, and the branch pipe 24 may have a simple arc shape or a curved shape including a plurality of arcs. In short, the oxygen sensor 30 is disposed at the end of the branch pipe 24 on the engine body 11 side. In addition, it is only necessary to be arranged offset to the inner peripheral side of the branch pipe 24 bent with respect to the axis 24 d passing through the center of the branch pipe 24.

  In the second embodiment shown in FIG. 8, the oxygen sensor 30 is disposed in the downstream branch pipe 62b. However, the present invention is not limited to this, and the oxygen sensor 30 corresponds to the endmost first cylinder 11A (see FIG. 6). More specifically, the downstream branch pipe 62a may be disposed at the end portion of the bent downstream branch pipe 62a on the engine body 11 side and offset from the axis of the downstream branch pipe 62a toward the inner peripheral side.

  In any of the first to third embodiments, the oxygen sensor 30 is installed in the branch pipe 24 or the branch portions 61, 62, 63 downstream of the intake chamber 22, but the intake air in the intake chamber 22 constituting the intake passage is used. You may install in the piping 17 side.

  The present invention is suitable for an oxygen sensor disposed in an engine intake device.

10, 50, 80 Engine 11, 81 Engine body 17 Intake piping 22 Intake chamber (collecting part)
24, 25 Branch pipe (branch passage)
24b bent part (bent pipe part)
24d Axis 28, 60, 90 Intake pipe 30 Oxygen sensor 61, 62, 63 Branch (first branch, second branch, third branch)
62a, 62b, 92a, 92c Branch pipe (downstream branch pipe)
91, 92, 93 Branch part (first branch part, second branch part, third branch part)
e Oxygen sensor offset

Claims (6)

In the sensor arrangement structure in which the sensor for measuring the air-fuel ratio in the intake air is arranged in the intake passage of the engine,
The intake passage is provided with an intake pipe provided on the upstream side, a downstream side of the intake pipe, and a plurality of branch pipes and each branch pipe communicating with each intake port of the engine to form a branch passage. Consists of intake manifolds with connected collection parts,
The intake pipe is arranged so as to be connected to the collecting portion from one side in the branch passage arrangement direction,
A sensor arrangement structure characterized in that a sensor is arranged in the intake passage on the one side, downstream of the intake pipe.   2. The sensor arrangement structure according to claim 1, wherein a sensor is arranged in the one of the branch passages.   The one-side branch passage is formed with a bent portion that is bent so as to project outward from the collecting portion toward the engine in the branch passage arrangement direction, and the sensor is more than an axis passing through the center of the branch passage. The sensor arrangement structure according to claim 1, wherein the sensor arrangement structure is arranged offset to an inner peripheral side of the bent portion.   The sensor arrangement structure according to any one of claims 1 to 3, wherein the sensor is arranged at a terminal portion near the engine in each branch passage.   2. The intake pipe comprising a plurality of branch passages is provided with a plurality of stages of branch parts, and the sensor is arranged at a branch part on the second and subsequent stages from the upstream side of the intake pipe. 2. The sensor arrangement structure according to 2.   6. The sensor arrangement structure according to claim 5, wherein the sensor is arranged in a branch pipe branched from the branch section in the second and subsequent stages, and is arranged in a branch pipe on a center side in the branch passage arrangement direction. .

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